The presently disclosed subject matter relates generally to video coding techniques and, more particularly, to video coding techniques involving the selection of a quantization parameter (QP) and/or a data rate based on motion-sensing circuitry.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Many video coding techniques, such as those outlined by standards such as MPEG-1, 2, and 4 and H.261, H.263, and H.264, achieve compression of video signals by removing redundant information. This information may include, for example, redundant temporal and/or spatial information in a series of video images. In addition, such video coding techniques may remove information that may otherwise by imperceptible to a user watching the decoded video. For example, one video coding technique may involve encoding a first video frame as a “key frame,” which may preserve substantially all information about the original video frame, and which may take up a significant amount of storage space. A series of subsequent frames may be encoded as “non-key frames,” which may include substantially only differences between the subsequent non-key frames and the key frame, and which may take up significantly less storage space.
During the encoding process, to relate the subsequent non-key frames to the key frame and previous non-key frames in decoding order, the subsequent frames may be predicted by the encoder based on information in the video frames. However, the predicted frames are unlikely to perfectly predict the actual video frame to be encoded. A difference between the original, uncompressed video frame to be encoded and the predicted frame may be referred to as prediction error. This prediction error may carry additional spatial details about the predicted frame. By applying a spatial transform to the prediction error, a corresponding decoder may obtain coefficients carrying spatial detail not present in the predicted frame.
Based on a desired video compression bit rate and a desired quality for a given frame, the encoder may apply a quantization parameter (QP) during the encoding process to the prediction error. The QP may represent one of a finite number of step sizes for use in transforming the prediction error. With a larger value of QP, the transformation may result in a video signal having a smaller number of bits. However, the video signal may produce a distorted image if the source video frame is particularly complex. On the other hand, smaller values of QP may produce more precisely reconstructed images, but may require a greater number of bits. Selecting a proper QP for encoding a current video frame may involve examining a series of future or prior video frames to predict motion in the frame. However, a system that lacks the capability to look ahead due to hardware limitations or practical considerations may be unable to select the proper QP in such a manner.